Let me put it this way. The generation generally starts to die when a new console from one of the major manufacturers is released - this event occurs at the same time for all manufacturers.
The PS3 and the XBOX360 will be hit by the downturn caused by the start of the next generation at the same time and it is therefore illogical to compare them in the way the OP does.
Imagine two people in a first to the finish running race where one person gets a five second head start. While the other person may run faster it doesn't mean they're going to cross the finishing line first.








